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    //! CPUID

    use volatile_register::RO;
    #[cfg(not(armv6m))]
    use volatile_register::RW;

    #[cfg(not(armv6m))]
    use peripheral::CPUID;

    /// Register block
    #[repr(C)]
    pub struct RegisterBlock {
        /// CPUID base
        pub base: RO<u32>,

        _reserved0: [u32; 15],

        /// Processor Feature (not present on Cortex-M0 variants)
        #[cfg(not(armv6m))]
        pub pfr: [RO<u32>; 2],
        #[cfg(armv6m)]
        _reserved1: [u32; 2],

        /// Debug Feature (not present on Cortex-M0 variants)
        #[cfg(not(armv6m))]
        pub dfr: RO<u32>,
        #[cfg(armv6m)]
        _reserved2: u32,

        /// Auxiliary Feature (not present on Cortex-M0 variants)
        #[cfg(not(armv6m))]
        pub afr: RO<u32>,
        #[cfg(armv6m)]
        _reserved3: u32,

        /// Memory Model Feature (not present on Cortex-M0 variants)
        #[cfg(not(armv6m))]
        pub mmfr: [RO<u32>; 4],
        #[cfg(armv6m)]
        _reserved4: [u32; 4],

        /// Instruction Set Attribute (not present on Cortex-M0 variants)
        #[cfg(not(armv6m))]
        pub isar: [RO<u32>; 5],
        #[cfg(armv6m)]
        _reserved5: [u32; 5],

        _reserved6: u32,

        /// Cache Level ID (only present on Cortex-M7)
        #[cfg(not(armv6m))]
        pub clidr: RO<u32>,

        /// Cache Type (only present on Cortex-M7)
        #[cfg(not(armv6m))]
        pub ctr: RO<u32>,

        /// Cache Size ID (only present on Cortex-M7)
        #[cfg(not(armv6m))]
        pub ccsidr: RO<u32>,

        /// Cache Size Selection (only present on Cortex-M7)
        #[cfg(not(armv6m))]
        pub csselr: RW<u32>,
    }

    /// Type of cache to select on CSSELR writes.
    #[cfg(not(armv6m))]
    pub enum CsselrCacheType {
        /// Select DCache or unified cache
        DataOrUnified = 0,
        /// Select ICache
        Instruction = 1,
    }

    #[cfg(not(armv6m))]
    impl CPUID {
        /// Selects the current CCSIDR
        ///
        /// * `level`: the required cache level minus 1, e.g. 0 for L1, 1 for L2
        /// * `ind`: select instruction cache or data/unified cache
        ///
        /// `level` is masked to be between 0 and 7.
        pub fn select_cache(&mut self, level: u8, ind: CsselrCacheType) {
            const CSSELR_IND_POS: u32 = 0;
            const CSSELR_IND_MASK: u32 = 1 << CSSELR_IND_POS;
            const CSSELR_LEVEL_POS: u32 = 1;
            const CSSELR_LEVEL_MASK: u32 = 0x7 << CSSELR_LEVEL_POS;

            unsafe {
                self.csselr.write(
                    (((level as u32) << CSSELR_LEVEL_POS) & CSSELR_LEVEL_MASK)
                        | (((ind as u32) << CSSELR_IND_POS) & CSSELR_IND_MASK),
                )
            }
        }

        /// Returns the number of sets and ways in the selected cache
        pub fn cache_num_sets_ways(&mut self, level: u8, ind: CsselrCacheType) -> (u16, u16) {
            const CCSIDR_NUMSETS_POS: u32 = 13;
            const CCSIDR_NUMSETS_MASK: u32 = 0x7FFF << CCSIDR_NUMSETS_POS;
            const CCSIDR_ASSOCIATIVITY_POS: u32 = 3;
            const CCSIDR_ASSOCIATIVITY_MASK: u32 = 0x3FF << CCSIDR_ASSOCIATIVITY_POS;

            self.select_cache(level, ind);
            ::asm::dsb();
            let ccsidr = self.ccsidr.read();
            (
                (1 + ((ccsidr & CCSIDR_NUMSETS_MASK) >> CCSIDR_NUMSETS_POS)) as u16,
                (1 + ((ccsidr & CCSIDR_ASSOCIATIVITY_MASK) >> CCSIDR_ASSOCIATIVITY_POS)) as u16,
            )
        }
    }

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